(1) Field of the Invention
The present invention relates to a system for indicating the presence of an obstacle, an aircraft equipped with this system, and an obstacle-avoidance procedure.
Thus, the invention lies within the technical area of obstacle detection on board an aircraft.
(2) Description of Related Art
The simplest and the most free manner of flying consists of piloting an aircraft by observing the outside environment in order to guide this aircraft and, if necessary, to avoid obstacles. The phrase “visual flight” characterizes this type of flying.
Visual flight is traditionally authorized under certain visibility and cloud-cover conditions. Such visual flight is governed by rules that are known by the abbreviation “VFR” (Visual Flight Rules).
During visual flight, however, a pilot may not see an obstacle, or may not see it early enough to avoid a collision, which could lead to an incident. These obstacles may include, in particular, electrical power-line pylons, antennas, cables such as electrical power lines, antenna guy wires, or even towing cables.
Poor awareness by the pilot of the presence of these obstacles is a recurring factor in accidents during visual flight.
Systems for determining the presence of obstacles are known. However, these systems may be considered costly, and therefore are not installed on board aircraft intended for visual flights. In fact, the instrumentation that is present on board such aircraft may be reduced in order to reduce the cost of the aircraft, which does not appear to be compatible with the installation of costly instruments for signaling obstacles.
Conversely, aircraft are instrumented in order to allow flight known as “instrument flight” In compliance with rules that are known by the abbreviation “IFR” (Instrument Flight Rules).
A pilot performs an instrument flight in compliance with these IFR rules with the aid of instruments and, optionally, with the aid of an airborne control center, in order to:                keep his aircraft in a proper flight configuration, in terms of altitude and speed;        follow a path imposed by the air traffic organizations; and        comply with the published regulations and procedures.        
An aircraft may be equipped with a system known by the acronym “TAWS” (Terrain Awareness and Warning System). The versions of TAWS systems that are dedicated specifically to being carried on board rotary-wing aircraft are sometimes known as “HTAWS”.
This TAWS system is used, in particular, within the context of instrument flights.
A TAWS system can allow a predictive operating mode based on the use of a database of terrain and of obstacles, if any. The system determines the presence of an obstacle by using this database and, if necessary, signals an obstacle to a pilot.
The term “terrain” is understood as referring to the surface of the planet. The preparation of a terrain database may cause certain obstacles that are present on the surface of the planet to be likened to terrain, such that these obstacles are not treated as obstacles but as terrain.
Accordingly, the term “obstacle” is understood as referring to an object that is located on the surface of the planet but that is not identified as constituting a part of this surface.
A TAWS system may, if appropriate, provide a reactive operating mode using sensors on board the aircraft to probe the outside environment and detect a potential obstacle. The detection of an obstacle leads to the triggering of a warning intended for a pilot. These sensors may include a variometer, a radio altimeter, or even a piece of equipment known in English as “glide slope”.
Thus, TAWS systems are designed primarily for use during IFR (i.e., instrument) flight. The function of a TAWS system is to warn the pilot of an estimated collision risk, based on relatively short notice. Accordingly, the goal of the TAWS system is not to provide long-term anticipation helping a pilot to acquire and maintain, during visual flight, visual contact with the potentially most dangerous obstacle.
The terrain and obstacle database is sometimes divided into a terrain database that provides topographic information and an obstacle database that lists potential obstacles.
The obstacle database or databases that are used in TAWS systems are subject to quality requirements and an expensive trackability process, particularly in view of their use during IFR (instrument) flight. They are then updated by competent organizations.
Furthermore, aircraft are sometimes equipped with an active detection system known by the abbreviation “OWS” (Obstacle Warning System). An OWS system may be based on the use of a probe device that probes the sector of the outside environment located in front of the aircraft. This probe device may include a radar, a so-called “scanning” laser, or a laser-based remote detection system known by the acronym “LIDAR” (“Light Detection and Ranging”) that employs a laser light. The echoes generated by the probe device could possibly permit reconstitution of the obstacles that are located in the detection zone.
Consequently, TAWS and OWS systems have the disadvantage of being expensive, because of the devices and/or the databases to be implemented. These TAWS and OWS systems may therefore be difficult to implement on board an aircraft intended for visual flight.
Furthermore, and in order to combat wire-based obstacles of the cable type, a rotary-wing aircraft may be equipped with one or more cable cutters.
Cable cutters are worthwhile and inexpensive passive solutions for preventing an accident following a collision with a cable. However, cable cutters are not effective against all types of obstacles, such as, for example, a crane.
Map-display systems only make it possible to view the position of topographic elements and of obstacles in relation to the position and orientation of the aircraft.
These map systems do not always necessarily include warning means for signaling an obstacle, and require an analysis of the display that can take the pilot several seconds to perform.
Document FR 2,780,701 proposes the inclusion of measurements of the instantaneous position and speed of an aircraft in messages that are broadcast via radio. A device installed on board a given aircraft flying VFR analyzes the messages that are broadcast via radio and the path being followed by this given aircraft in order to identify a collision risk. A potential collision risk is signaled vocally.
Document FR 2,893,158 describes a procedure for the construction of a database of obstacles that includes topographic information about obstacles based on heterogeneous sources. Among these sources, document FR 2,893,158 cites commercial databases that include topographic data about obstacles, or even information from various organizations that are responsible for compiling the obstacles.
Document U.S. Pat. No. 7,994,902 B2 proposes an anti-collision system in which vehicles on the ground send and receive GPS information for anti-collision purposes.
Documents EP2355071, EP 2407953, FR 2,908,218, EP 0911647, EP 2204639, U.S. Pat. No. 7,633,430, US 2009/082954, and US 2013/169541 are also known.
Thus, the goal of the present invention is to propose an innovative and, if possible, inexpensive system for indicating the presence of an obstacle in an aircraft and, possibly, in an aircraft engaging in visual flights.